ABSTRACT

The basis of vibration analysis consists of deriving a predictor equation from recorded vibrations as a function of distance and explosive charge weight. There are several unresolved issues in this approach and they continue to be the subject of extensive research. These include near-field vs far-field recording, distinction between short and long charges, determining the vibration limit for blast-induced damage in rock, and the use of ‘seed waveform’ in controlling vibration amplitude (Holmberg and Persson, 1978; Hustrulid and Wenbo, 2002). In deriving predictive curves for limiting blasting vibrations, the concept of explosive weight per delay remains central. It is based on the assumption that all the holes firing within a nominal 8 millisecond delay interval must be considered cumulative in terms of the total charge weight. The usual firing time scatter characteristic

1 INTRODUCTION

The use of blasting vibrations, and the peak particle velocity in particular, has become indispensable in providing guidelines for safe blasting in terms of minimizing damage to residential structures (Dowding, 1996; Oriard, 1999). It is also being used increasingly to investigate the performance of the explosives used in the blast (Mohanty and Yang, 1997). The characteristics of blasting vibrations depend critically on the amount of explosives detonated at any given time, the delay intervals employed in the blast design, and the prevailing geological conditions. Of course, optimised delay between holes and rows gives better fragmentation and lower vibration levels (Singh et al., 1996). The proper combination of explosive weight and delay timing is such that which allows sufficient room for expansion of the rock mass (swelling) between rows in multiple row blasts. Such restrictions in

of pyrotechnic detonators on one hand, and precision of the electronic detonators on the other, make this assumption highly subjective (Farnfield and Yuill, 2001; Mohanty and Wong, 2004). The inapplicability of the 8-ms rule has been demonstrated by several researchers in the past (Anderson, 1989; Moore and Richards, 2002).